Steam generator and the like



Sept. 18, 1928. ifiMfiYfi J. TAIT STEAM GENERATOR AND THE LIKE Filed May 5, 1927 LN JP l2? b nfofi Patented Sept. 18, 1928.

JOHN TAIT, 01' PORT GEALMERS, NEW ZEALAND.

STEAM GENERATOR AND THE LIKE.

Application filed Kay 3, 1927, Serial No. 188,572, and in Great Britain June 4, 1926- This invention is for improvements in or relating to steam generators and the like and has for one of its objects to provide for a-more efiicient transfer of heat taking place. The invention is particularly applicable to boilers for generating steam, but it is also applicable to other devices in which flame-tubes or the like are providedthrough which heat ing gases are passed in order to transfer their '0 heat to water or other material surrounding the tubes. It is well known that heating devices of this nature as heretofore constructed are not particularl efficient and it is also an established fact t atthe transfer of heat [5 from the interior to the exterior of flametubes decreases in efficiency from the inlet end towards the outlet end.

The present invention relates to steam generators or the like of the kind having a taw pered flame-tube which is reduced in c1rcumference and cross-section towards its outlet end compared with its inlet end as distinct from the more usual construction in which these tubes are of uniform diameter throughout their length. The invention is characterized by the fact that the reduction in the bore of the tube is so proportioned as either to keep the velocity of gas-flow through the tube constant throughout the length of the tube or to increase it from the inlet end towards the outlet end, the gas-flow being reckoned, say, in feet per second at a 'ven point. It will be appreciated that this arrangement is different from the usual practice with parallel tubes which is to secure a gradual reduction in the speed of the The effect is an increased eificiency 0 heat transfer, more particularly at the cooler ends of the tubes.

The magnitude of the reduction in the cross-sectional area of the flame-tube will depend upon circumstances. For instance, if the absolute temperature of the gases entering the fiame-tu e from the fire grate 'is about double the absolute temperature of the water in the boiler, then in order to keep the gas-flow at least constant throughout the length of the tube the crosssectional area at the inlet end should be double the cross sectional area at the outlet end.

In applying the invention to multi-tubular flame-tube boilers of usual types the ditnculty arises that the tubes are required to be of the smallest diameter at the ends where provision is usually made for access to the tubeplate for removal of the tubes. For example, in boilers of the marine type in which the tubes return from a combustion-chamber at the back of the boiler towards the smoke stack at the front of the boiler, the tubes according to the present invention must be ta-, pered so that they are smaller at the front end, and in boilers of this type the removal of the tubes must take place from the front end. Similarly, in locomotive boilers the removal of the tubes must take place from the front. The reason is the same in both cases, namely that the combination chamber from which the tubes conduct the furnace gases is a confined space insufficient to admit the full length of a boiler tube.

The invention comprises a flame-tube tapercd as above described which is provided at its smaller end with an enlargement of such external diameter as to fit a tube-plate the aperture in which is large enough to pass the large end of the tube.

The actual construction and arrangement of the tapered flame-tubes accordin to the invention will differ in diiferent installations;

The accompanyin drawing shows a vertical cross-section trough a multi-tubular marine-type boiler.

Referring to the drawing the cylindrical shell of the boiler is indicated at 14., the furnace shell at 15 and a wet-back header-compartment at 16. One side of the header-compartment 16 comprises a tube-plate 17 and the front of the boiler comprises a tube-plate.

18 opening into an uptake flue 19. These parts are of usual construction. Between the plates 17 and 18 there extends a-series of flame-tubes 20 which are tapered so as to be smaller in cross-sectional area at the end where they are secured in the plate 18 than at the end where they are secured in the plate 17. In order to facilitate insertion and removal of the tubes, the holes for receiving them in the plate 18 are made the same size as the holes in the other tube-plate 17, or

they may be a little larger. The ends of the tubes 20 adjacent to the plate 18 are either enlarged to form a bell-mouth, as shown at 21, or are provided with an external collar 22, either or both types of tube connections above described may be used in the same boiler. The size of the enlarged bell-mouth or of the exterior of the collars is sufiicicnt to make a fit in the tube-plate 18.

It will be understood that in both the boilers described the reduction in cross-sectional area of the fines or flame-tubes must be such as under the normal conditions of working of the boiler will lead to the velocity of gasflow through them bein kept constant or increased as it passes along the tube. The known laws of heat-transmission through the walls of tubes, at given rates of flow of furnace gases therethrough enable the actual reduction of diameter required in given conditions to be readily calculated.

By securing a more efiicient interchange of heat, the present invention will enable installations to be made more compact since the desired results can be obtained with shorter flame-tubes than has heretofore been considered necessary.

I claim v 1. In a multi-tubular flame-tube boilerthe combination of tapered flame-tubes which at their smaller ends are provided with enlargements the diameter of which is greater than that of the larger ends of the flame-tubes and a tube-plate into which the said enlargements are fitted, substantially as and for the purpose set forth.-

2. In a multi-tubular flame-tube boiler the.

combination of tapered flame-tubes which at their smaller ends are provided with bell- Inouths the diameter of Which is greater than that of'the larger ends of the flame-tubes and atube-plate into which the said bell-mouths are fitted, substantially as and for the purpose set forth. 7

3. A flame-tube for use in a boiler or the like as claimed in claim 1, which is provided with a short bell-mouth at the small end for the purpose described. a

4. In a multi-tubular flame tube boiler the combination of a fire-box, a smoke-box, a nest of tapered flame tubes which extend from the fire-box to'the smoke-box and which are of larger diameter at the end nearest the fire-box, taper uniformly and smoothly to the smoke-box and are each provided where they fit the tube plate of the smoke-box with an enlargement, the diameter of which is greater than that of the large end of the taper of each tube so that theholes in the tube plate become lar e enough to permit the withdrawal of eac tube from the nest small end first.

In testimony whereof I JOHN TAIT.

aflix my signature. 7 

